The insertion of terminal phosphinidene complexes into the bh bond of amine and phosphine boranes

Push-pull complexation: Transient terminal phosphinidene complexes [RP?W(CO)(5) ] insert at 110?°C into the B?H bonds of L?BH(3) (L = Et(3) N, Ph(3) P; see scheme). The reaction is probably driven by an interaction between the nucleophilic boron and the electrophilic phosphorus.     

Alkyne hydrothiolation catalyzed by a dichlorobis(aminophosphine) complex of palladium: selective formation of cis-configured vinyl thioethers

Cis all round: Dichlorobis[1-(dicyclohexylphosphanyl)piperidine]palladium, [(P{(NC(5)H(10))(C(6)H(11))(2)})(2)Pd(Cl)(2)], is a highly efficient alkyne hydrothiolation catalyst and the first generally applicable system that selectively generates cis-configured anti-Markovnikov adducts in excellent yields within only a few minutes at 120?°C in the presence of only 0.05?mol?% of the catalyst (see scheme).     

An Expeditious Route to Eight-Membered Heterocycles By Nickel-Catalyzed Cycloaddition: Low-Temperature C sp 2C sp 3 Bond Cleavage

A cool break: 3-Azetidinone and a variety of diynes undergo a cycloaddition reaction catalyzed by Ni/IPr to give dihydroazocine compounds (see scheme; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolidene). The reaction involves a challenging C?sp?2?C?sp?3 bond cleavage step, yet, surprisingly, proceeds at low temperature.     

Copper-Catalyzed Aerobic Dehydrogenative Cyclization of N-Methyl-N-phenylhydrazones: Synthesis of Cinnolines

O(2) leading the way: The title reaction proceeds through an oxidation/cyclization sequence, thus representing the first copper-catalyzed coupling reaction of hydrazones through a C?sp?3?H bond functionalization process (see scheme; DMF=N,N'-dimethylformamide, Py=pyridine). The method provides an environmentally friendly and atom-efficient approach to biologically active cinnoline derivatives.     

CN Bond Cleavage and Ring Expansion of N-Heterocyclic Carbenes using Hydrosilanes

Ring expansion of NHCs! The reaction of N-heterocyclic carbenes (NHCs) with hydrosilanes Ph(4-n) SiH(n) (n=1, 2, 3) results in complete rupture of the heterocycle and silylene insertion into one of the C?N bonds of the carbene (see scheme; R=alkyl, aryl).     

Selective Iodine-Catalyzed Intermolecular Oxidative Amination of C(sp(3) )H Bonds with ortho-Carbonyl-Substituted Anilines to Give Quinazolines

Access to quinazolines: The selective amination of C(sp(3) )?H bonds adjacent to nitrogen or oxygen atoms of N-alkylamides, ethers, or alcohols with ortho-carbonyl-substituted anilines constitutes the first step in a tandem annulation that leads to quinazolines in good to excellent yields (see scheme; NIS=N-Iodosuccinimide, TBHP=tert-butyl hydroperoxide). The selectivity of the amination of primary and secondary C?H bonds is also noteworthy (left: >3:1, right: >99:1).     

Carbon(sp(3) )Fluorine Bond-Forming Reductive Elimination from Palladium(IV) Complexes

Pd(IV) -fluoride complexes, some of which are remarkably insensitive to water, have been synthesized and used in the title reaction, which proceeds with high selectivity to give the product of the C(sp(3) )?F coupling (see scheme, TfO=trifluoromethanesulfonate). Preliminary mechanistic studies implicate a pathway involving dissociation of pyridine followed by direct C?F coupling at the Pd center.     

Radical Polymerization of the Silene (Me3Si)2SiCR2 by Hydrogen Transfer from a Trimethylsilyl Group

The silene (Me₃Si)₂Si?Ad is polymerized to produce a polycarbosilane with an unusual Si? Si? C repeating backbone, rather than the Si? C or Si? Si? C? C units expected for olefinic radical polymerization. The polymer structure and the polymerization mechanism (see scheme) were studied by GPC, EPR, and NMR spectroscopy and by trapping experiments.

     

Metallic impurities in graphenes prepared from graphite can dramatically influence their properties

All at C? Graphenes prepared by the top-down exfoliation of graphite are shown to contain metallic impurities (see scheme, metal impurities shown as black dots). These impurities may dominate their properties and can have a negative influence on their potential applications.     

Structure formation and catalytic activity of DNA dissolved in organic solvents

Equal-opportunity dissolver: By attaching polyethylene glycol at its 5' end, DNA (PEG-DNA) can be solubilized in various organic solvents and was shown to form G-quadruplexes by CD spectroscopy. A complex containing iron(III) protoporphyrin?IX (hemin) and G-quadruplex-forming PEG-DNA catalyzed an oxidative reaction in methanol (see scheme).     

Synthesen,chemische Reaktionen und NMR-spektroskopische Untersuchungen substituierter Phosphonopyruvate

Phosphonopyruvates: Syntheses, NMR Investigations, and Reactions The new 3-(diethoxyphosphoryl)-2-oxopropanoates 5–24 and -propanamides 25–38 with various substituents at C(3) were prepared in moderate-to-good yields (Schemes 2 and 3, Tables 1 and 2). It was shown that they adopt a preferred conformation in which the diethoxyphosphoryl group and the substituent at C(4) are antiperiplanar to each other (see B ). The keto-enol tautomerization of phosphonopyruvates with Ph? C(3) (see 20 ) and MeS? C(3) (see 24 and 33 ) was examined. In CHCl₃, two tautomeric species exist, whereas in dimetylsulfoxide (DMSO), three tautomeric forms are observed. Oxime ethers, an oxime, and a phenylhydrazone of unsubstituted phosphonopyruvates were prepared (see 40–44 ), and quinoxalin-2(1H)-ones could be obtained from the reaction of pyruvates with 4,5-dimethylbenzene-1,2-diamine (see 45–47 ).     

Organocatalytic, asymmetric synthesis of 3-sulfenylated N-boc-protected oxindoles

Sulfenylated oxindoles: The first asymmetric sulfenylation of N-Boc-protected oxindoles has been developed to provide products containing a tetrasubstituted stereogenic center in high to excellent yields (86-98?%) and, in most cases, excellent enantioselectivities (up to 96?%?ee; see scheme).     

Synthesis of Highly n-Type Graphene by Using an Ionic Liquid

n-Type graphene: A new, easy, and cheap method to produce n-type reduced graphene oxide was developed by synthesizing a partially reduced intermediate containing nitrogen (PrGO-IL, see scheme) by treating graphene oxide (GO) with an ionic liquid (IL) at 160?°C followed by rapid thermal annealing (RTA) at temperatures ranging from 400 to 1000?°C. A high N-doping level of 6?% was achieved and the N-doped rGO exhibits n-type behavior with a Dirac point at -38?V at 400?°C.     

Mg-catalyzed enantioselective benzylic C-H bond functionalization of isoindolinones: addition to imines

Access to chiral isoindolinones: The Mg-catalyzed enantioselective benzylic C-H bond functionalization of isoindolinones is described. A Bu(2) Mg/Schiff base catalyst (1:1) promoted the enantioselective addition of N-Boc-isoindolinones to aryl, heteroaryl, alkenyl, and alkyl imines, giving 3-substituted isoindolinones in 84-99?%?ee and 50:50-91:9?d.r. (see scheme).     

Treatment of Naphthols with B(C(6)F(5))(3): Formation and Characterization of the Lewis Acid Adducts of Their Keto Isomers

With the strong Lewis acid B(C(6)F(5))(3), the keto tautomers from a variety of naphthol derivatives are obtained (e.g. alpha-naphthol, see scheme). The adducts of the tautomers were characterized by X-ray structure analysis, and the first attempts at hydrozirconation of the adducts were made.     

Isomerization of Aldehydes Catalyzed by Rhodium(I) Olefin Complexes

A mixture of isomeric aldehydes is formed in a catalytic isomerization of alkyl aldehydes with [C(5)Me(5)Rh(olefin)(2)] complexes. This process offers an indirect method for altering the n:iso ratio of aldehydes formed in hydroformylation reactions. For example the reaction of n-butanal with [C(5)Me(5)Rh(CH(2)=CHMe)(2)] (1) results in the formation of a bis-alkyl carbonyl rhodium complex 2 which is the resting state during the isomerization of n-butanal to a mixture of n- and iso-butanals (see scheme). In the presence of other olefins transfer formylation is observed.     

First Higher‐Order Photocycloaddition to a CN Bond: 1,3‐Diazepines from Maleimides

A light touch is all that is required to cleave a maleimide C? N bond to effect a [5+2] photocycloaddition with a sterically encumbered C?N moiety (see scheme).

     

Total synthesis of the bacterial RNA polymerase inhibitor ripostatin b

A modular and highly stereoselective synthesis of the title compound was developed. Key steps in the assembly of the carbon framework of ripostatin?B (1; see scheme) were a stereoselective Paterson aldol reaction and a high-yielding ring-closing metathesis mediated by Grubbs first generation catalyst. The C15 hydroxy group was established through Tishchenko-Evans reduction in excellent yield and selectivity.     

An asymmetric aerobic aza-wacker-type cyclization: synthesis of isoindolinones bearing tetrasubstituted carbon stereocenters

It's all in the solvent: An enantioselective variant of an aza-Wacker-type cyclization that gives isoindolinones containing tetrasubstituted carbon centers α to the nitrogen atom has been developed (see scheme; tfa=trifluoroacetate). The use of a highly coordinating solvent is crucial for the activity of the catalyst and the stereoselectivity the reaction (up to 99?%?ee).     

Selective construction of Pd2Pt and PdPt2 triangles in a sandwich framework: carbocyclic ligands as scaffolds for a mixed-metal system

Sandwich time! The mixed-metal triangular-trinuclear sandwich complexes of Pd(2)Pt and PdPt(2) were selectively synthesized. The Pd(2)Pt and PdPt(2) triangles in a cycloheptatrienyl sandwich framework were identified by (31)P?NMR analyses of the tris-triphenylphosphine complexes (see scheme).